Is it useful to recall Adam Smith's genuine, 14-carat DEFINITION of 'real  
wealth' as 'the annual produce of the land and labour of the society'? By  
doing so we relate it immediately to modern macroeconomic measures such as  
GDP, equally applicable to either reason mentioned by Gunning. For, in his  
second case,  if market prices accurately reflect relative marginal  
utilities (and if we follow Hicks in assuming that we always observe  
variables in the neighbourhood of their equilibrium values)  a putative net  
welfare gain or loss must show up in the (constant price) National Accounts.  
If prices do not reflect relative marginal utilities there's no point in  
Welfare Economics at all. 
 
As an afterthought: it was also Adam Smith who first insisted that  
'Consumption is the sole end and purpose of all production; and the interest  
of the producer ought to be attended to, only so far as it may be necessary  
for promoting that of the consumer'. 
 
Anthony Waterman